An Introduction To Extreme Cooling

Computer enthusiasts have options for several different types of aftermarket cooling to get those last few MHz out of a system, the most common of these being a high end heatsink and fan.

The next step, if you’re still hungry for more speed, is a water cooling setup. But for many of us, water cooling is far too limiting for pushing our hardware even close to its limitations. This is where extreme cooling comes in. By lowering the temperature of our components, we are able to reach clocks far beyond the limits allowed by air or water cooling.

But there are several methods of taking your components to subzero temperatures, based on your purpose, goals, and finances. With options to cool from only a few degrees under freezing all the way to near absolute zero, in this article I will attempt to explain several of these extreme cooling methods. It will serve as an introduction to more in-depth guides on extreme cooling I will be writing in the coming weeks.

For all of these extreme cooling options, great care should be taken so you don’t get your components wet. Condensation or melting ice can fry a motherboard without warning – a single drop is all it takes. But if you’re careful, taking your components cold can be extremely rewarding. The next article for the extreme cooling category will be a guide on getting everything safely insulated.

The first type of extreme cooling (on a temperature scale) is thermoelectric cooling, or TEC.

A TEC is a solid state device which works by transferring heat from one side to the other and is used in combination with a water or air setup to remove the heat dumped to the ‘hot’ side of the TEC module. This type of cooling adds no additional noise to your cooling system, but little additional benefit. It can provide a few degrees of cooling power over water, but with the added risk of condensation and it uses a lot of energy. I think many people would agree with me that adding TEC to an air cooling setup is a waste of time and money and most likely will stress the heatsink beyond its design limits.

This is what a TEC module (or peltier) looks like:

The next type of extreme cooling is called phase change, and includes a few different types of coolers based on vapor phase change refrigeration principles. A phase change system can be used for 24/7 cooling as long as care is taken with insulation. But since these systems use a compressor and fans, they can be fairly loud, depending on the unit.

The first phase change cooling option is a water chiller. A basic water chiller places the evaporator from an air conditioning unit into a reservoir with the fluid that is then pumped through an existing water cooling system. The tubing should all be insulated and a substance with a much lower freezing temperature than water should be used.

The second type of phase change cooling I’d like to discuss is called single stage. A single stage phase setup uses the same principle as a basic air conditioner, but replaces the evaporator (the part that gets cold on the a/c unit) with a copper block that sits directly on the CPU or GPU. This is also called direct-die. Single stage units can cool anywhere from a few degrees below freezing to -40°C for a nice unit, to well below that for units by very experienced and knowledgeable builders. A single stage system uses a single compressor and loop for refrigerant.

If a single stage setup is still too warm, you may want to consider having a cascade system built. Much more complicated (and expensive) than a single stage cooler, a good cascade can hold temperatures below -100°C for hours of benching fun.

Using the same evaporator-on-die principle as a single stage, a cascade can make use of multiple compressors and refrigerants to achieve much colder temperatures. There are different types of cascades which will be discussed in an upcoming article. I don’t see a reason to use a cascade for 24/7 cooling, as it’s very loud and uses large amounts of power.

Here’s a picture I borrowed from Chris Morrell of a single-stager he built:

The options up to this point have been pretty much ‘set it and forget it,’ and require little attention other than initial setup. With the exception of the cascade, they are great for 24/7 use. However, these next three require near-constant attention and should never be considered for full time use.

Dry Ice, Liquid Nitrogen, and Liquid Helium can all be safely used (rather than more volatile substances like liquid oxygen) for extreme cooling. In these cases, an aluminum or copper tube sits directly on the CPU (or GPU or RAM) and is filled with the cooling substance of your choice. These pots can vary tremendously in design and cooling ability. Each of these cooling substances has it’s own benefits and drawbacks.

This is what one of these setups looks like:

Dry ice (frozen CO2), frequently referred to as DI or DICE, cools to a temperature of around -70°C. Dry ice comes in blocks or pellets and can be purchased at many grocery stores. You can store it in a cooler for a short time, but it needs to be used relatively soon after purchasing. The dry ice is crushed and mixed with acetone to provide a uniform cooling substance for the evaporator pot. It maintains a constant temperature (minus swing from CPU load) and one can get by just fine benching DI without a thermometer. It’s very easy to use and a great cooling method for someone just getting into extreme benching, as well as for the seasoned professional.

Liquid nitrogen, also called LN2 or nitro, cools to around -196°C. Used in a variety of medical and industrial applications, although it is not quite as readily available as DI, LN2 is still fairly easy to obtain. Many welding shops and medical gas supply companies have LN2 on tap or can deliver a pressurized 160L tank.

The storage device for liquid nitrogen is called a dewar, and may be pressurized for easy dispensing, or unpressurized on the smaller dewars, which can easily be poured into a thermos. In most situations a thermometer is essential when cooling with LN2, since maintaining a constant temperature is vital when a cold bug (the temperature at which a component no longer operates – this can vary widely even between seemingly identical CPUs) is present. Because of this, having a pot with more surface area and mass makes maintaining a constant temperature much easier.

Liquid helium, or LHe, has only recently started being used for CPU cooling, due to its high cost and extremely cold temperature. With a boiling point of around -269°C, it is the closest thing we have to bringing our components to absolute zero. LHe is only used on CPUs with absolutely no cold bug, such as AMD’s Phenom II stuff. It’s safe to make the assumption that few overclockers will ever have the opportunity to cool with this substance.

With so many options for taking your cooling to the extreme, I see little reason not to. It’s easier now than ever to get into this aspect of overclocking, since there is so much information available to get even the most timid of overclockers pushing out extreme benchmark scores in no time. Obviously, experience with air or water cooling is essential. Extreme cooling may seem intimidating at first, but anyone willing to dedicate the time and effort can do it.

This is a picture of me using LN2 on the CPU and a single stage on the northbridge, just to show it can be fun to combine all sorts of cooling methods to suit your needs. This setup was a Pentium 4 631 I overclocked to over 7.5 GHz.